Not everyone has flash plugins installed (I don't on ANY of my computers)
Not everyone has a cable connection (modem users will hate you)
Not everyone likes music and flashing graphics - I hate it personally

If you want to reach the largest audience, go with what has been a proven marketing/media device for centuries - black text on a white (light) background - newspapers, magazines are this way for a reason. Being forced to site through an animation is like watching commercials on TV. I just want the info, and then get out. I definitely wouldn't use it in a business site (unless you're targeting kids).

In my opinion I really like flash and looks professional to me, if the website was done right. Here in the US I think like 70% of the people have internet(correct me if I am wrong) and out of that percent I bet 25% have broadband(dsl, cable) . I haven't had a 56k connection in a long time but I do remember visiting flash websites and it didn't take that long to load the webpage.